1. Field of the Invention
The present invention relates to an automotive air conditioner and, more particularly, to an automotive air conditioner suitable for use on an automobile that has no heat source like a heat engine, such as an electric motorcar.
2. Description of the Prior Art
Referring to FIG. 18, a conventional automotive air conditioner is provided with a blower 2 disposed within a duct 1 to generate air flow through the duct 1. The air flowing through the duct 1 is cooled by an evaporator 3 to provide cool air. The cool air is heated by a heater core 4, which uses hot water as its heating medium, disposed downstream of, as after the evaporator 3, with respect to the flowing direction of the cool air. The mixing ratio of air that flows through the heater core 4 and air that bypasses the heater core 4 is regulated by an air mix damper 5 disposed near the heater core 4 to mix the air heated by the heater core 4 and the air bypassed the heater core 4 properly to provide air of a desired temperature.
This automotive air conditioner necessarily needs hot water, such as hot engine cooling water to heat air by the heater core 4. Accordingly, the automotive air conditioner is unable to reheat air properly when used on an automobile not having any hot water source, such as an electric motorcar, and hence it is difficult for the automotive air conditioner to control the temperature of the air to be blown into the passenger compartment properly.
Another conventional automotive air conditioner controls the temperature of air to be blown through an evaporator and a duct into the passenger compartment for cooling operation by interrupting the operation of a compressor instead of using the heater core 4. However, since the compressor of this automotive air conditioner is driven by the engine of the automobile, the interruption of the operation of the compressor changes the load on the engine sharply, sacrificing the comfort of the passengers.
A third conventional automotive air conditioner controls the temperature of air cooled by the evaporator 3 by varying the discharge capacity of the compressor in addition to the interruption of operation of the compressor. However, the operating speed of the compressor cannot be controlled independently of the operating speed of the engine because the compressor is driven by the engine.
The compressor of a domestic air conditioner, for instance, is controlled for constant operation. The domestic air conditioner is installed rarely so that cool air is blown directly toward the human body and hence the domestic air conditioner does not control the temperature of cool air to be blown into the room. A domestic air conditioner provided with an inverter or the like for controlling the operating speed of the compressor detects thermal load on the basis of the difference between the room temperature and a set temperature and controls the operating speed of the compressor according to the thermal load.